Fuel efficiency for trunk piston four-stroke diesel engines

ABSTRACT

The present invention relates to a system (and corresponding method) for reducing fuel consumption in a four-stroke trunk piston diesel engine, the system comprising: a replenishment system connected to receive engine oil from a four-stroke trunk piston diesel engine and to receive replenishment oil, where the replenishment system is configured for mixing the engine oil and the replenishment oil resulting in a mixed oil that is introduced into the engine.

FIELD OF THE INVENTION

The invention relates to a system for reducing fuel consumption in afour-stroke trunk piston diesel engine. Further, the invention relatesto a method of reducing fuel consumption in a four-stroke trunk pistondiesel engine.

BACKGROUND OF THE INVENTION

Diesel engines used onboard certain types of vessels and/or used incertain stationary applications are typically of the well knowntwo-stroke type or of the well known four-stroke type.

Two-stroke cross-head engines used in marine and/or stationaryapplications are equipped with two separate lubricating oil systems. Onelubricating system comprises so-called system oil/system lubricant thatnormally is used for lubrication and cooling of the engine's bearingsand e.g. oil-cooled pistons as well as for activation and/or control ofvarious valves or the like. The other lubricating system comprises anall-loss lubricant (cylinder oil/cylinder lubricant) that normally isused for lubrication of the engine's cylinders, piston rings and pistonskirt.

Four-stroke trunk piston diesel engines, however, typically use only asingle oil type for lubrication and cooling. Such engines are typicallyused as secondary/auxiliary or propulsion engines on ships, or instationary power generation or liquid/gas transmission applications.Such oils typically have a SAE viscosity of about 30 or 40.

Trunk piston engine oils are constantly affected by exposure to thecombustion process whereby the useful properties of the trunk pistonengine oil is degraded over time as the oil become more and more spentuntil finally the oil will have to be either replenished or completelychanged. This degradation process cannot be reversed or halted byseparators or the like.

Contaminations caused by engine and part wear, particle pollution (e.g.from combustion by-products), oxidation, hydrolysis, etc. furtherdegrade the quality of the oil over time in addition to the oildegrading simply from being used, which speeds up the degradationprocess. The degradation process in effect increases the viscosity ofthe engine oil. A diesel engine's frictional loss is mainly of a viscosecharacter. An increase in the viscosity of the engine oil will thereforeresult in diminished operating efficiency, increased fuel consumption,decreased engine efficiency, increased component wear and increasedemissions.

The performance level of the oil is typically measured periodically andmay not go beyond certain limits if the oiled component's conditionshould not be jeopardized. When the engine oil is approaching itscondemning limit it will have to be replenished or changed. Changing theoil is usually done by de-bunkered the oil, which is a costly process,or storing the oil as waste for later burning resulting in emissions.

To prolong the usable time of oils used in such engines, suitedadditives and/or additive packages are added to the base oil in order toobtain a fully formulated oil. Such blending is typically done atdedicated land based blend plants and the fully formulated oil has tothe delivered to a ship or an off-shore plant for use in the engines.The addition of additives or additive packages increases the cost of theengine oil significantly.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system for and acorresponding method of reducing fuel consumption in a trunk pistondiesel engine that solves the above-mentioned (and other) shortcomings.A further object is to provide this in a cost-effective and simplifiedway that requires little modifications of existing systems.

These objects, among others, are achieved by a system for reducing fuelconsumption in a four-stroke trunk piston diesel engine, the systemcomprising: a replenishment system connected to receive engine oil froma four-stroke trunk piston diesel engine and to receive replenishmentoil, where the replenishment system is configured for mixing the engineoil and the replenishment oil resulting in a mixed oil that isintroduced into the engine.

Since the degradation process of the engine oil effectively is slowed byreplenishing it the above mentioned adverse effects of the degradationprocess are reduced or slowed or even avoided in a simple way. Thus, thereplenishment system provides enhanced and consistent performance of theinitial engine oil resulting in greatly reduced component wear andequipment lifecycle cost. Even further, a more environmentally friendlysystem is provided since less waste in the form of spent oil is producedas the usability period of time for the engine oil is prolonged.

Further, the normal engine oil need not contain so many additives sinceit is replenished whereby cheaper engine oil (since it do not need tocontain additives or additive packages) can be used without compromisingthe efficiency of the engine.

The efficiency of the engine is also increased as it in a longer periodof time uses oil having a lower viscosity.

Thus great economical savings and environmental improvements areachieved.

Further, the addition of a replenishment system according to the presentinvention only requires minor adaptation of existing systems.

In one embodiment, the replenishment system comprises a mixing unitreceiving the replenishment oil and the engine oil and mixing themaccording to a predetermined rate resulting in the mixed oil.

In one embodiment, the replenishment system is configured for mixing theengine oil and the replenishment oil on a continuous, near-continuous orintermittent basis.

In one embodiment, the replenishment system is configured forintroducing the mixed oil to the engine on a continuous, near-continuousor intermittent basis.

In one embodiment, a rate for mixing the engine oil and thereplenishment oil is dependent on at least one measured actual conditionof the oil, where the rate of mixing is automatically adjusted inresponse to the at least one actual condition of the oil.

In one embodiment, the replenishment oil comprises one or more additivesand/or additive packages comprising one or more selected from the groupof a Calcium detergent, an alkali metal detergent, an alkali-earth metaldetergent, an anti-wear additive, a dispersant, a friction modifier, andanti-oxidants

In one embodiment, the engine is used in marine or stationaryapplications.

In one embodiment, the engine is used offshore, on-site or in a landbased plant.

In one embodiment, the replenishment oil is selected from the group of:

-   -   a heavy fuel oil,    -   bunker oil, and    -   residual fuel oil.

The present invention also relates to a method reducing fuel consumptionin a four-stroke trunk piston diesel engine, which corresponds to thesystem of the present invention.

More specifically, the invention relates to a method of reducing fuelconsumption in a four-stroke trunk piston diesel engine, the methodcomprising the steps:

-   -   receiving engine oil from a four-stroke trunk piston diesel        engine and receiving replenishment oil in a replenishment        system, and    -   mixing the engine oil and the replenishment oil resulting in a        mixed oil that is introduced into the engine.

Advantageous embodiments of the method according to the presentinvention are defined in the sub-claims and described in detail in thefollowing. The embodiments of the method correspond to the embodimentsof the system and have the same advantages for the same reasons.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the illustrative embodiments shown in thedrawing, in which:

FIG. 1 illustrates a schematic block diagram of a prior art four-stroketrunk piston engine system;

FIG. 2 illustrates a schematic block diagram of a four-stroke trunkpiston engine system according to one embodiment of the presentinvention; and

FIG. 3 illustrates a schematic block diagram of a preferred embodimentof a replenishment system according to one embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a schematic block diagram of a prior art four-stroketrunk piston engine system. Shown is a typical prior art four-stroketrunk piston engine (100) connected to its oil system responsible forcycling oil through the engine during use thereby cooling andlubricating the engine (100) and other parts of the system.

Oil being tapped from the engine (100) is typically passed through afirst filter (110) by a pump (not shown) or the like where the filter(110) is responsible for removing small particles, insolubles, weardebris, etc. from the oil. After this, the oil is passed to an engineoil container (101) or the like. Connected to the oil container (101) isa separator or filter (111) (forth only-denoted separator) that receivessome of the oil from the container (101) and removes dirt, wear debrisfrom engine components, water caused by hydrolysis, etc. typically byspinning. The separator (111) may also remove unwanted chemicalcompounds like CaSo₄, etc. The resulting unwanted materials are removedfrom the system as waste or sludge.

Oil is taken from the oil container (101) and passed through anotherfilter (112) removing small particles, insolubles, debris, etc. andwater and other materials of different density SG e.g. the same or, aspreferred, a different technique (e.g. using a centrifuge mechanism)than the first filter (110) before being introduced into the engine(100) for use again.

As mentioned earlier, the oil is degraded by this process causingdecreased engine efficiency, increased fuel consumption, etc. When theoil is approaching its condemning limit it will have to be replenishedor changed and is discarded as waste and stored for later de-bunkeringor burning.

FIG. 2 illustrates a schematic block diagram of a four-stroke trunkpiston engine system according to one embodiment of the presentinvention. The illustrated system comprises a four-stroke diesel pistonengine (100), a first filter (110), an oil container (101), a separator(111) and another filter (112) connected and corresponding to the onesshown and described in connection with FIG. 1.

Further shown is a replenishment system (102) according to an embodimentof the present invention. The replenishment system (102) is connected toreceive some of the engine oil after leaving the engine (100) e.g. via athree-way valve (113) or some other flow and/or rate controlling means.

Preferably, the replenishment system (102) receives engine oil after ithas proceeded through the separator (111) so it is cleaner than if itwas tapped directly from the oil container (101). Alternatively, thereplenishment system (102) could receive engine oil directly from theoil container (101) whereby the three-way valve (113) is not needed orfrom another place in the engine system.

The replenishment system (102) mixes replenishment oil (e.g. heavy fueloil (HFO), residual fuel oil, bunker oil or the like) received from anadequate source (like a container, tank or the like) with the receivedengine oil thereby creating a mix of oil (103) that effectively is lessspent as it is mixed with fresh or fresher oil. The mixed oil (103) isthen introduced Into the engine in addition to the engine oil beingintroduced normally as described in connection with FIG. 1 from the oilcontainer (101).

The mixed oil (103) may be supplied to the engine (100) on a continuous,near-continuous or intermittent basis.

In one embodiment, the replenishment oil (HFO, residual fuel oil, bunkeroil, etc.) also comprises one or more additives and/or additivepackages. The additives may e.g. comprise a Calcium detergent, alkalimetal(s) detergent(s), alkali-earth metal detergent(s), anti-wearadditives, dispersants, friction modifiers, anti-oxidants, etc.improving the engine/system condition and/or efficiency in some way oranother.

The replenishment system (102) may be configured for mixing the engineoil and the replenishment oil on a continuous, near-continuous orintermittent basis.

Since the degradation process of the engine oil effectively is slowed byreplenishing it the above mentioned adverse effects of the degradationprocess are reduced or slowed or even avoided. Thus, the replenishmentsystem provides enhanced and consistent performance of the initialengine oil resulting in greatly reduced component wear and equipmentlifecycle cost. Even further, a more environmentally friendly system isprovided since less waste in the form of spent oil is produced as theusability period of time for the engine oil is prolonged.

Further, the normal engine oil need not contain so many additives sinceit is replenished whereby cheaper engine oil (since it do not need tocontain additives or additive packages) can be used without compromisingthe efficiency of the engine.

The efficiency of the engine is also increased as it in a longer periodof time uses oil having a lower viscosity.

Further, the addition of a replenishment system according to the presentinvention only requires minor adaptation of existing systems.

The engine (100) according to the present invention can e.g. be used inmarine or stationary applications, both on-shore and off-shore.

FIG. 3 illustrates a schematic block diagram of a preferred embodimentof a replenishment system according to one embodiment of the presentinvention. Shown is an engine system corresponding to the one in FIG. 2with the addition of a more detailed embodiment of the replenishmentsystem (102). In this embodiment, the replenishment system (102)comprises a mixing or blending unit (114) (forth only referred to asmixing unit) or the like that receives the engine oil via the three wayvalve (113) from the separator (111) (or alternatively directly from theoil container (101) and fresh (or at least less spent oil than theengine oil) heavy fuel oil (HFO), bunker oil, residual fuel oil, etc.The mixing unit (114) mixes the HFO and the spent engine oil resultingin the less spent mixed oil (113) that is introduced into the engine(100).

The mixing unit (114) can be any standard mixing unit capable of mixingoils at the required rates

In a preferred embodiment, the rate of mixing is dependent on at leastone measured actual condition of the oil. The measured condition coulde.g. be the pollution level or condemning level of the engine oil. In apreferred embodiment, the rate of mixing is automatically adjusted inresponse to at least one actual condition of the oil that preferablyalso is measured automatically and provided to the mixing unit (114).

A holding tank (104) or the like may be Inserted between the mixing(114) and the rest of the engine system (101/111). This holding tank(104) may act as a reservoir of engine oil coming from the separator(111). This may be useful if the rate of introducing the mixed oil (113)into the engine is not the same as the rate of engine oil passingthrough the separator (111). Further, since additional oil is added tothe system thereby increasing the total volume of oil it may benecessary to have extra storage capacity if the oil container (101) isnot of an adequate size.

An additional tank (105) may also be inserted after the mixing unit(114) for holding the mixed oil (113) before it is introduced into theengine (100). The additional tank (105) may e.g. be a ‘day’ or holdingtank that is emptied into the engine whenever operations requires it,which simplifies the process of introducing the mixed oil (103) into theengine. Other rates of Introducing the mixed oil (113) into the enginemay be just as applicable.

In this way, the typical degradation process of the engine oil is slowedby replenishing it the adverse effects associated with the degradationprocess are reduced or slowed or even avoided in a very simple way.Thus, the replenishment system provides enhanced and consistentperformance of the initial engine oil resulting in greatly reducedcomponent wear and equipment lifecycle cost. Even further, a moreenvironmentally friendly system is provided since less waste in the formof spent oil is produced as the usability period of time for the engineoil is prolonged. Additionally, great economical savings andenvironmental Improvements are achieved.

In the claims, any reference signs placed between parentheses shall notbe constructed as limiting the claim. The word “comprising” does notexclude the presence of elements or steps other than those listed in aclaim. The word “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements.

1. A system for reducing fuel consumption in a four-stroke trunk pistondiesel engine, the system comprising: a replenishment system connectedto receive and to replenish an engine oil from a four-stroke trunkpiston diesel engine and to receive a replenishment oil, where thereplenishment system is configured for mixing the engine oil and thereplenishment oil resulting in a mixed oil that is introduced into theengine, and wherein the replenishment system comprises a mixing unit forreceiving the replenishment oil and the engine oil, and for mixing thereplenishment and engine oils according to a predetermined rate toobtain the mixed oil.
 2. (canceled)
 3. A system according to claim 1,wherein the replenishment system is configured for mixing the engine oiland the replenishment oil on a continuous, near-continuous orintermittent basis.
 4. A system according to claim 1, wherein thereplenishment system is configured for introducing the mixed oil to theengine on a continuous, near-continuous or intermittent basis.
 5. Asystem according to claim 1, wherein the rate for mixing the engine oiland the replenishment oil is dependent on at least one measured actualcondition of the oil, where the rate of mixing is automatically adjustedin response to the at least one actual condition of the oil.
 6. A systemaccording to claim 1, wherein the replenishment oil comprises one ormore additives and/or additive packages comprising one or more selectedfrom the group of a Calcium detergent, an alkali metal detergent, analkali-earth metal detergent, an anti-wear additive, a dispersant, afriction modifier, and anti-oxidants.
 7. A system according to claim 1,wherein said engine is used in marine or stationary applications.
 8. Asystem according to claim 1, wherein said engine is used offshore,on-site or in a land based plant.
 9. A system according to claim 1,wherein the replenishment oil is selected from the group of: a heavyfuel oil, bunker oil, and residual fuel oil.
 10. A method of reducingfuel consumption in a four-stroke trunk piston diesel engine, the methodcomprising the steps: receiving an engine oil from a four-stroke trunkpiston diesel engine and receiving a replenishment oil in areplenishment system, mixing the engine oil and the replenishment oil bya mixing unit thereby obtaining a mixed oil, wherein the mixing unitreceives the replenishment oil and the engine oil and mixes thereplenishment and engine oils according to a predetermined rate toobtain the mixed oil; and introducing the mixed oil to the engine. 11.(canceled)
 12. A method according to claim 10, wherein the replenishmentsystem mixes the engine oil and the replenishment oil on a continuous,near-continuous or intermittent basis.
 13. A method according to claim10, wherein the replenishment system introduces the mixed oil to theengine on a continuous, near-continuous or intermittent basis.
 14. Amethod according to claim 10, wherein the rate for mixing the engine oiland the replenishment oil is dependent on at least one measured actualcondition of the oil, where the rate of mixing is automatically adjustedin response to the at least one actual condition of the oil.
 15. Amethod according to claim 10, wherein the replenishment oil comprisesone or more additives and/or additive packages comprising one or moreselected from the group of a Calcium detergent, an alkali metaldetergent, an alkali-earth metal detergent, an anti-wear additive, adispersant, a friction modifier, and anti-oxidants.
 16. A methodaccording to claim 10, wherein said engine is used in marine orstationary applications.
 17. A method according to claim 10, whereinsaid engine is used offshore, on-site or in a land based plant.
 18. Amethod according to claim 10, wherein the replenishment oil is selectedfrom the group of: a heavy fuel oil, bunker oil, and residual fuel oil.